1. Field of the Invention
The present invention relates to a holding and sealing material of a catalytic converter for purifying an exhaust gas discharged from an internal combustion engine or the like.
2. Discussion of the Background
As shown in FIG. 5, conventionally, a catalytic converter 90 for purifying an exhaust gas has been used for purifying an exhaust gas discharged from an internal combustion engine 92 or the like. The catalytic converter 90 has a catalyst carrier 1, a shell 95 made of metal and covering the outside of the catalyst carrier, and a holding and sealing material 91 which is set between the both. The holding and sealing material 91 can prevent the exhaust gas from leaking out from between the catalyst carrier 1 and the shell 95, and also, it can prevent the catalyst carrier 1 from damage in contact with the shell 95.
At a time of manufacturing the catalytic converter 90, the holding and sealing material 91 is wound around the catalyst carrier 1, and the wound unit is set within the shell 95. Then, an inlet connection 97 and an outlet connection 98 are respectively connected to both ends of the shell 95 by welding. The catalytic converter 90 manufactured in the manner mentioned above is set in the middle of a pipe 99 for an exhaust gas discharged from the engine 92.
As the holding and sealing material 91, the material made by infiltrating a mat-like material 911 made of alumina-silica based ceramic fibers (inorganic fibers) or the like with an organic binder 912 has been used. Because the holding and sealing material 91 is an aggregate of filaments and its specific gravity is small, there is a risk that a part of the inorganic fibers flies in all directions in the air from a surface of the holding and sealing material 91 at a time of manufacturing the catalytic converter 90 by mounting the holding and sealing material 91 in the catalyst carrier 1 and the shell 95. Therefore, there is a risk of deteriorating a working environment of a working area for the mounting work, and it is necessary for a worker to work with wearing an antidust mask or the like.
For the prevention of the inorganic fibers flying, alumina fibers aggregate whose average fiber diameter and minimum fiber diameter are controlled to specific range has been developed so far (refer to Patent document 1). When the alumina fibers aggregate is assembled to the catalyst carrier 1 and the shell 95 as the holding and sealing material 91, it is possible to reduce a flying amount of inorganic fibers (alumina).
However, it was impossible to adequately reduce a flying amount of inorganic fibers even by a conventional holding and sealing material 91 whose fiber diameter is controlled. Therefore, there is a risk that a part of the inorganic fibers flies in all directions in the air while at work and a working environment is deteriorated.
[Patent document 1] JP 2003-105658 Unexamined Patent Publication (Kokai)